I think Messenger Plus! is a great add-on to MSN Messenger and for me, and most of my friends, it was the only reason why we started using MSN Messenger.
I like all the features Messenger Plus! has right now and honestly don't know what we could add to it at the moment.
I, personally wouldn't have a problem if MsgPlus 3.6 was the last major update as long as you would not drop it completely. That means, if there are new really great new features to be added or improved at some time that that will be done.
One thing that I'm afraid of is that this great MsgPlus! community that built up around the Messenger Plus! program will collapse at some point, because fewer new members will join and the older ones will leave once they finally found a life.
My hope is that Messenger Plus! will continue to evolve just as MSN Messenger does, when they introduce new features, we will certainly find new features that can be added, or ways to improve MsgPlus!.
I would love to see Messenger Plus! and it's community to develop further because I can't see a limit right now, as I said when MSN adds more features to their program there will be new possibilities for Messenger Plus! to enhance them and to add even cooler ones.
I would sure hope to see Messenger Plus! 4.5 along with MSN Messenger 8 sometime in the future.
Really, MSN Messenger isn't the same without Plus!.
But in the end it is your own decision, if you think you can't continue Messenger Plus! anymore and want to tackle new projects, do so.
Btw, my guess is that MSN asked you to join their MSN Messenger dev team