Want and should is the thing. I want and want to believe that Arsenal progress to a point where they can win the league but I guess my expectation is that I don't think they can whoever is in charge because of the financial state of the game. It's possible of course but extremely unlikely. For all of their progress this season, I don't think Spurs will get near it next season either. I don't feel I am being defeatist or wanting to coast along (and I think there are more than a few who feel that way).
Spurs are the anomaly at the moment but they still have a lot to prove. Poch has done amazingly well by buying strong, young hungry players but the next few seasons are the real test. It's also taken them decades of rubbish to get to this point. I said in another post that Arsenal certainly missed a lot of great players when they became available in the last few years which is disappointing but then everyone's scouting is awesome now so.
I would have liked to see a change this season because I have great respect for Arsene and hate to see the hate he is getting but also as you said, the club needs something fresh.
I do think that Arsenal and Arsene will improve next season though. I don't think the formation change was just a psychological change for the team. Some players who's form had been poor for some time started to flourish and look like the players they should be. I hope Arsene sticks with it.
You say you don't think it's possible but Spurs have shown that it is. They might not have won the League but the 86 points they got would have won them the League in a lot of other seasons.
And what gives you the confidence to believe things will improve next season? What's going to change? You mention the new system but hasn't Wenger all but said it was a short term fix and he prefers playing 4 at the back so he can have an extra midfielder?