“Eventually they're going to want to do a migration from that partner bank to the acquired bank,” said Stephen Greer, senior analyst at Celent. “That is essentially a core migration effort because you're moving customer accounts from one legacy bank to another legacy bank. These tend to be long and arduous and can take years.”

While the acquiring bank is focused on the account migration, competitors are expanding their product offerings.

“You have the likes of Chime and other independent neobanks coming up with early payday lending or credit-builder cards and all of these things that have made them really attractive and lucrative to the types of customers that they're trying to attract,” Greer said. “And then you're just behind at that point.” Also, outages and technical issues are common during core migrations.

“The risk is that if you buy one of these startups, how do you ensure that once you start to merge the technologies, you're still delivering on the product road map, delivering value to consumers and ensuring that it's a consistent experience and that there aren't significant outages?” Greer said.