u mean whole existing bitcoins address and the keys to be in network ?
Yes, I guess.
I'm no expert and I don't know if it is possible.
The idea is just that it would have the same blockchain until block X and from then on become a parallel blockchain. All addresses and keys would be identical, but after block X I assume it would only make sense to give each fork its own life (payment in one is not a payment in the other).
If you own 10 BTC before block X you will after have both 10 BTC and 10 BTC-2.0.
I believe such an altcoin would quickly die unless it offers some very good advantages. On the other hand, if one day there really is a need for a better protocol (e.g. turns out bitcoin addresses can be hacked), then maybe something like this will be the solution.