I am in the process of testing WAAS with WCCP. I have a 7206VXR at the core, where a cluster of WAE's will live.
In my remote offices, I have a range of 2800's, 3700's, and 2620's (non XM).
From other posts, I have seen where the minimum recommended IOS is 12.4(10).
Right now, the 7206 is 12.3(22). I can upgrade it if need be, but it is stable. The 3700's and 2800's are minimum 12.4(10). The 2600's are another story. They are 12.2(40), and obviously cannot go to 12.4.
Will I need to upgrade the 7206?
Will the 2600's work well, or should I consider PBR or Inline for those?
12.3(22)* and 12.2(40) are both fine from a WCCP perspective. However, you should consider using inline interception with the 2600's and they will become a performance bottleneck once WAAS is deployed.
* Note that WCCP in 12.3 code does not redirect fragments.