1- For inbound traffic from the Internet, that will be possible if you use F5 GTM (I am a Cisco person when it comes to routers and switches but anti-cisco when it comes to Firewall, load balancers and other things, I just things there are better vendors out there than cisco); however, you will NOT be able to maintain previously traffic flows. New traffics will be re-directed to the new DC by the GTM but existing traffic flows will not be maintained. If you think about it, that makes perfect sense.
2- for outbound traffcs, assuming that you have your routing design properly, this will work as well. If both ASAs in DC1 fail, the server will know how to use multi-gigabit link between the DC and go out of ASA on DC2; however, since the ASA is "stateful" firewall, any previously initiated traffics will be lost, only new connections will work; if you want to maintain previously traffic flows, it will be possible with routers (without firewall) because routers can handle asymetric routing (or maybe ASA can handle as well with tcp-bypass feature) but I don't think it will work either because in this design, the destination servers is expecting you're coming from the same IP address (NAT'ed I assume) in both DCs. when DC1 is down and you're using DC2, you will be using a different NAT'ed, thus breaking previous traffics flow. Is it possible, yes? Difficult to achieve, hell yes.
