I read the MEPAG report "Robotic Mars Exploration Strategy 2007 - 2016" (which actually covers mission possibilities out to 2020). It's somewhat surprising in that it makes no mention whatsoever of a high resolution camera of a MOC or HiRISE class in that entire period. MRO is designed to last a long time, maybe 10 or 12 years if we're lucky. Its replacement is the proposed Mars Science and Telecommunications Orbiter for 2013, which is favored to carry an atmospheric science payload (which I agree is long overdue). The highest resolution camera proposed for MSTO is a MARCI class clouds and dust monitoring imager.
With a Mars sample return suggested as the first mission of the 2020's (and one or more Mars launch opportunities may have to be sacrficed to pay for it), an orbiter to replace MSTO couldn't be launched until at least 2022. That would most likely leave a gap of several years without a functioning high res camera in Mars orbit (unless European or Russian). Does anyone else feel that this is a major oversight on the part of MEPAG and NASA? There were 9 years between the launch of MGS and MRO, but no HiRISE replacement is envisioned for more than 15 years. This is way out in the future, I know, but these things have to be planned many years in advance. Any thoughts on this?
BTW, the same situation applies to CRISM.