Arsenal may be looking but the fact is average time a manager stays at a club is under two years these days. Ancelotti's contract is for 4,5 years so if he stays that long it will be way longer than the average. We will have built a new stadium by the time his contract runs out.
He is a brilliant man-manager and tactically flexible. He understands that tactics must be dictated by the players available. Hopefully his name also helps recruit better players. I'm not sure how much weight that has but maybe at least in situations where other factors are pretty even. Many world class players also credit him for improving them.