There is no guarantee that Comcast will actually provide DVR recordings in the cloud or if they do when it will be available to every customer. Currently, Comcast is doing a small scale test of this in Boston.
For example, the TiVo interface was ported to the Motorola DVRs years ago and was offered to customers in the New England area. This option was never expanded beyond the New England area. Now, Comcast has a deal with TiVo to allow certain TiVos to access Video on Demand, but its in only a few markets.--
Cisco RNG 200N & SA 8300 HD DVRs-S26 Guide