Though I perked for a Pro1X, I doubt that it will be much of an improvement for daily usage, except the more stanardised QWERTY.
But I think there is a good chance for more (security) updates on the Pro1X, so that might prolong its life time. As I expect it might be many years before we see a new alternative.
On the Cosmo, you should rather have a look at their successor the Astro, it seems an overall improvement. The sliding (like most previous sliders except the Nokias) will require a balanced push to open, but should not posse a serious problem. The larger keys might making typing