The Russians have three choices.

1. Push a peace initiative.

2. Resist the current Ukrainian offensives with available resources, and continue the war of attrition.

3. Mobilize and start a major offensive.

Putin has already stated that Germany has crossed a red line. NATO equipment is on the border of Russia. Russia can easily deploy Brigade tactical groups, just as Ukraine has, that are self sufficient and move like gangbusters. Attacks from the north of Kharkow to isolate the city. Byelorussia might become involved, permitting attacks toward Kiev or Lvov. Direct attacks on the Ukrainian forces in Luhansk. I believe the blitz is coming.