For the past several years, the only games I've played in have been d20. Furthermore, I now don't really have the time to be bothered learning new systems, and especially new systems that don't serve any good purpose. So, unless the designers of a new game have a good reason for not using d20, I feel they should do so.
So, my answer would be 'Yes', I could be satisfied if d20 was all there was. However, that would not be my preference... since there are some cases where a non-d20 system is preferable. Additionally, I have found that there is a 'D&D mindset' that seems to creep in whenever players are doing anything d20, which makes certain genres (notably horror) extremely difficult to run effectively. So, although d20 can do horror (IMO), I don't think I would ever try using it for that purpose.