WebAccess - Many apps are moving to be web-based. This seems to me like a critical place to put alot of energy. Potentially, it can eliminate the use of the client all together, right? I've used Gmail heavily for years and have been very surprised how well I do without a mail client. I've been surprised how many Google Apps users are quite happy with it as well. I really think that everyone (including Mac and Linux) will be happy if WebAccess is robust enough.
AD Support & WebAdmin - I've heard from a few customers in the last year asking about if/when AD will be supported.
Outlook and 3rd-Party Integrations - This seems like a big dance between the two. In my mind, it isn't realistic to think you can effectively do both really well. So you we need a good long-term strategy. I definately agree with Joe Marton that the Cx0 likes Outlook. I also know that many third-party apps plugin to Outlook. Is it feasible for them to tie into GroupWise as well via Outlook? I'm certainly not an expert in this area. There certainly is a need to be able to have third-party integrations.
Mobility - This is critical. If there isn't a good mobility solution, GroupWise will not maintain market share. Period.