As far as Jacobs he needs to use this momentum and get back in the ring ASAP. He earned the respect of boxing fans around the world so take advantage of that. The worst thing he can do is sit on the sidelines for a year like we've seen so many other fighters do in the past. He may not be able to get an immediate rematch with Golovkin because of reasons discussed below, but he can use this positivity to advance his career. Ending Golovkins 23 knockout win streak alone gets respect, and winning rounds and being in a very competitive, close fight throughout is a big accomplishment for him. A Hopefully he can stay active, get right back into ring.
K2 had been planning and working on a fight for June in Kazakhstan for the final middleweight title, the WBO belt which is owned by Billy Joe Saunders. We all know GGG longtime goal has been to unify all the major belts in the division - WBA, WBO, IBF, WBC and The Ring belt. He has just one more to go and Saunders apparently is willing to fight him in Kazakhstan so can't really blame them if that's what happens next. And of course they want Canelo after that in September. So if that all happens and obviously Jacobs wont get an immediate rematch so again he needs to stay active. But if Saunders bitches out again which he might considering he already turned down Golovkin twice, as well as turning down Jacobs last year, then Jacobs may just get that immediate rematch after all.
Btw, Hopkins is the only man in middleweight to unify all fove major belts, Golovkin if he beats Saunders will be one of three people in all of boxing in any division to do the same:
Hopkins and his five belts (six including the IBO which no one considers as a legit belt but Golovkin has this one as well).