Yes, the easy upgrade path offered by AMD makes it tempting to jump in but it is also an easier way to burn a hole in your pocket.
By an upgraded AM3 board £100+
Wait and buy a new AM3+ Motherboard with 9 Series chipset when released £???
Wait and buy a new AM3+ CPU when they are finally released £?
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Or wait a little while and just buy a new AM3+ CPU and AM3+ 9 series Motherboard when they come along and you will probably save over £100 and be future proofed for at least 2 - 3 years.