Is it posible to create a transaction output that can either be reddemed by privK of Addr A or by privK of Addr B AFTER certain blockheight?
Certainly. You can do this with OP_CHECKSEQUENCEVERIFY which allows for relative timelocks.

The basic structure would look something like this:

IF
    &lt;pubkey A&gt;
ELSE
    "30d" CHECKSEQUENCEVERIFY DROP
    &lt;pubkey B&gt;
ENDIF
CHECKSIG


Read BIP 112 for more information.