When Chase started offering the new Marriott Premier Plus card it offered the old card members an upgrade offer which was too low for some members.
Those who waited to upgrade have some good news as they seem to have changed their offer.
The below link can be used to check offers:
I got 50k and upgraded instantly as I need to hoard 240K points before Dec 31. Please keep in mind that there are reports that you wouldn't get the 15 nights credit if you haven't gotten in the previous card. You would also lose the ability to earn bonus nights for every 3k in spend. You do get a slightly better earnings structure as you get 6pts / $ at Marriott, SPG properties compared to 5 and 2 everywhere else compared to 1.