Hi,
I've noticed in the videos at www.fulldeflection.com that all the top
aerobatic aicraft, such as the Sukhoi SU-31, Egde 540, Extra 300,
etc., can almost hover.

It seems that within a few years they will be able to climb on power
alone.

Aerobatics will look completely different once that occurs. Can you
imagine Svetlana Kapanina hovering her Sukhoi for a couple of minutes
at 300', then reversing down to an even lower altitude. I can imagine
Peter Besenyei performing the perfect square shaped hover in his Extra
540.

Is this technically feasible, or have the aircraft already reached a
developmental limit ?

Superdoof.