Hot new restaurants in London?
Depends on what you are looking for/how much to spend etc and how new you're keen on plus whether you want to travel from Piccadilly.
The best two new openings in London this year are Pollen Street Social and Roganic in my opinion (I've not been to Dinner).
Pollen Street Social is a short walk from Piccadilly and is a superb new restaurant from Jason Atherton who ran Maze. It's very innovative, but in a fine dining way. I've no idea on your budget but if you're looking for a really nice dinner (you'd probably spend close to £100pp including wine, service etc) then I think Pollen Street fits the bill.
Roganic is not that near Piccadilly, it's a good half hour walk. It is a superb new restaurant though with fascinating foraged ingredients. Much less formal, less of a 'fine dining' feel to it and very casual but I loved it. Not cheap either - you'd spend more than £125pp if you had the full tasting menu with wine.
Other new restaurants near Piccadilly which are a bit less formal and less expensive but equally fun are the Opera Tavern and Spuntino (from the Polpo group).
Pollen Street Social
10 Pollen St, London, England W1S 1, GB