The highly unusual relationship was underscored by the countless missives, described by Trump as "love letters," that the two men exchanged during Trump's four years in office.

Biden, on the other hand, has been brutal in his criticism of Trump's engagement with Kim, which according to the president-elect weakened US sanctions.

Biden called Kim a "thug" during the last presidential debate and has been highly critical of North Korea throughout the entirety of this year's presidential campaign.

It's unclear what comes next for Biden. He has outlined his priorities on entering the White House and North Korea does not feature, nor is a meeting likely any time soon. Unlike Trump, Biden has made it clear he would be unwilling to sit down with Kim without preconditions.

Experts are split as to whether North Korea will feel the need to do the same for Biden.

"The North Koreans often telegraph what they're going to do," said John Delury, an associate professor at Seoul's Yonsei University.

"If you listen carefully to their statements they usually indicate where they are heading, and I would say there's been almost no signals that they're planning a major provocation or test."

As Yun points out, these are different times for Kim -- and a missile test might not be as high on his agenda as it was four years ago.

"They now have proven that they have a viable ICBM (intercontinental ballistic missile) that can reach almost anywhere in the continental US, they also have a very big nuclear device which they tested in 2017," Yun said.

North Korea also has a number of its own pressing issues to contend with. The coronavirus, which Kim claims has yet to infect any of his people, a struggling economy as sanctions continue to pinch, and recovery from a string of typhoons and flooding earlier this year.

What comes next

Biden knows the challenges likely posed by North Korea. Pyongyang conducted both a nuclear and a long-range missile test in the opening months of Obama's presidency, under which Biden served as vice president.

However, he is not necessarily expected to revert back to the Obama-era policy of "strategic patience" of waiting for Pyongyang to come to the negotiating table while keeping sanctions in place.

That policy failed to achieve its main objectives. during that time, North Korea significantly expanded its nuclear and missile capability and carried out four of its six nuclear tests.

Ambassador Yun said that Biden has shown he "wants a diplomatic solution, he wants an engagement."

"Sure, he has emphasized denuclearization, but at the same time he has emphasized what he called principled diplomacy so I would hope that the engagement door would be more open now," he said.

However, a provocation from Pyongyang -- especially a missile test -- could dramatically change the calculus for a Biden administration.

Evans Revere, senior director with the Albright Stonebridge Group, has extensive experience negotiating with North Korea during his time at the State Department. He believes Biden would react strongly to any provocation from North Korea.

A response will most likely include the immediate resumption of large-scale US-South Korea military exercises, new military deployments to Korea and the surrounding area and a major effort to impose new sanctions and strengthen existing measures, said Revere. "As well as to take new steps designed to isolate, weaken and pressure the North Korean regime," he added.

It is not clear at this time what pressure China, North Korea's main trading partner and ally, would exert to prevent a resumption of testing. It's also not clear how a US-China relationship, currently at its lowest point in years, would progress.

Trump's personal style may have led to three history-making summits, but nuclear talks between the two countries have been stuck in neutral for months.

Diplomacy with North Korea will likely be much more process oriented, said Delury of Yonsei University.

"Under Trump what we've seen is a personalistic style which is almost unprecedented," he said. "A Biden administration is going to be an administration, there's going to be a coherence to it."

The era of summits may be over ... for now

Biden has not ruled out meeting with the North Korean leader but only "on the condition that he would agree that he would be drawing down his nuclear capacity."

Pyongyang has doled out its fair share of insults to Biden over recent months, calling him a "fool of low IQ" and a "rabid dog" who "must be beaten to death with a stick."

But former US officials who have dealt with Pyongyang acknowledge name-calling is par for the course. Trump himself has shown us threats and insults do not rule out diplomacy.

President Obama warned an incoming President Trump that North Korea would be one of the most pressing national security concerns.

Revere believes Biden does not need any such warning.

"He understands the problem and knows that, after four years of the Trump administration, the North Korean nuclear threat is greater than ever," Revere said.

"Biden is not about to ignore North Korea, and Pyongyang can be counted on to ensure that he doesn't."