Strictly is notorious for having a perceived 'wrong' winner - it goes way back! Most of the time, it's a valiant trier who triumphs over the better technical dancers, because that's what the public loves - Darren Gough winning over Colin and Zoe, Tom Chambers over Rachel and Lisa, or Chris Hollins winning over Ricky Whittle. The occasions where the genuine best dancer in the competition has actually won are fewer, IMO. Jill, Alesha, Kara and Harry are perhaps the only ones who's strong ability completely matched their public popularity at the time of their finals.
I still think Jay most likely has the combination of public support and is genuinely an incredible dancer - but this is actually a strong year, where Georgia and Kelly are both very, very good all-rounders, and could easily produce individual dances to rival Jay's ones. When you also factor in Katie's public support, and her lovely to watch, elegant ballroom that seems to keep the public voting for her time and time again, this is actually a very close final. IMO, that's good for the show. It encourages people to tune in, and the viewing figures usually go up when there is an element of potential surprise in the results.
BTW, I remember the Tom Chamber's semifinal debacle well. That issue, I'm convinced, propelled him to that win. The perceived injustice and the other two labelled as 'judge's favourites' ensured that he was a 'plucky underdog' and the audience rewarded him for that and a crowd-pleasing showdance. It all happened in a very compressed time period - I don't think there's been anything like that at this point in the competition (the Peter/Jamelia 'fix-gate' was quite some time ago). The media has tried to recreate that sensationalist type of headline on a weekly basis since then, so endless articles over 'fixes' are par for the course every single week now! But none of them are real public outrages. So we have a final with 4 celebs, 3 of whom have each been in the 3 most recent dances-offs. Unless Jay absolutely bombs his routines, I don't see anything that Kellie, Katie or Georgia produce make such a significant different that Jay doesn't win. At this point in the competition, pure public voting is the only time we see 'true' fair play - what the public wants, they will get. So, in the regard, it's fair!