I think it has to be 30% faster than M1. Otherwise its stagnant. And, judging by the history of all A chips (M is built on A architecture), all A chips do increase their performance 30% between series. So this is what I expect (and hope) will happen.It's simpler than that. M2 = more efficient = better battery life.
Also iPad is really not so fast that it cant be faster. It just depends how heavily are you abusing it.
And Apple should work to stay ahead of the game here, too.