ASUS has stated that they are making BIOS upgrades to some motherboards to make them AM3+ compatible (my sig motherboard included). I can even download the Beta BIOS right now, but there is always risk when flashing your BIOS and making a chipset work with updated sockets.
If it were me, I would get any of the 9XX series chipset motherboards. One reason being that the ASUS board does not have USB 3.0 or SATA 6.0Gb/s at all. My advice would be to future proof your computer as much as your budget allows (without sacrificing quality). ASUS, in my experience, makes very good boards. I just can't recommend using the 7XX series chipsets for Bulldozer (since we have no idea whether there will be a performance loss or not). BD is being made with the 9XX series in mind, so that's what you should go with if you are going Bulldozer.
Hope this helps!