Actually, I think Nokia made a very successful press in this MWC, without announcing EOS, Catwalk or the Verizon 920 variant. It's simply not the time to do it, but releasing 720 and 520 means they have already placed a complete product line for WP8, which is within only in half a year. From 520 to 920, we already see various combination of specs and market positions. L920, as the flagship, is still starting to pick up the numbers in many new markets, and its specs are still very competitive to others. And Verizon's market is not Europe. It makes no sense to release its variant in the show.
With these thinkings, Nokia has no need to release any flagship at the moment. So far, WP8 is pushing a lot of phones with similar specs and same apps to the market. Even for Nokia, the only major difference in their line is the camera. We can use the same drive, music, or map apps on different phones. Unless MS is playing the same game like Google on Android (release new features/systems but kick old phones out of update list), I don't think they will release brand new phones too soon on the same platform.