Well. Allegri had more than respectable results in UCL. His biggest letdowns was the big games in serie A in which his record was downright awful. But we approached those big UCL games with great preparation and respect and he might get out that with you too. Unless you believe bono.
But apart from some good games I did not in four years ever see his plan or style. what was his team and philosphy? I don't know, despite seeing 90% of our games (including friendlies) First years it was all this talk about pressing, but that was only seen in some stretches of games, then by the third season we seemingly just gave that up.
another problem here might be that he alienated himself with all the "winners" and mentally strong players in the squad and that Galliani kept on getting us players that wasn't that. that would be Chiellini, Pirlo, Tevez and Vidal in your team (although Tevez have his brain defects).
I think you will be fine for next year unless you lose those players you dread (I am less sure that you will actually lose many at all) andmight even improve in UCL. After that I expect you to become worse year by year unless you make really good transfers.