The main event has kicked off tonight. Russian forces (not seperatist) pushing forward on Ukrainian positions around Luhansk. Russian jets also active in Ukrainian airspace.
It's not really the main event until the tanks start rolling towards somewhere other than the existing front of the "breakaway republics", or bombing outside those regions start. If the Russians make a play for Kharkiv or Kyiv, it's on.
It's clear that the sword is poised, and I can't recall a situation where eleventh-hour diplomacy resulted in a country at this level of readiness backing off. If all Putin is looking for is something he can sell as a 'W', he can seize Luhansk and Donetsk, claim that the rest of the forces were to contain a possible Ukranian response elsewhere, and walk away.
I don't think that's likely. The disposition of forces pretty much screams out that he's going to make a play for Kharkiv and Kyiv, though they could just be there to force Ukraine to divide its military rather than respond in strength to the eastern incursion.
It's not clear to me whether the assets in Crimea are just there to hold the line, or to cut off resupply lines to Luhansk and Donetsk and assist in mopping up everything east of the Dnieper. It doesn't look like enough to make a play for Odessa. I think he's staying east of the Dnieper in the short run.