I think with Davis going it just made the choice clearer to let things go all at once and move on to different things.

Thing is, even if you had a Tennant willing to come back on, no reason to really other than specials, it would not be enough. You would need good stories and decent writing.

It would make the Doctor more enjoyable to watch but the stories would still not be good.

Which is how I sort of felt about the Smith era. Great Doctor but some of the stories were a bit too complicated and were focused onto things that made little sense to me. Or were just trying to be too meta for me. Or focusing too much on the companion at the expense of the Doctor, although that got worse after 11.