Depending on how long the situation continues in Ukraine and if it deteriorates further, Wizz Air will have around 22 slot pairs a week they will have free this summer...
This number also includes the slots to Moscow and St Petersburg, as UK airlines are banned from flying to Russia. Wizz Air are unlikely to be able to get around the ban on flying to Russia with Hungarian registered aircraft, as the UK/Russia bilateral agreement is to only allow 2 UK and 2 Russian airlines to operate between the two countries. With BA and Wizz being the two UK airlines.
All routes to Russia and Ukraine from Luton were operated by Wizz Air UK aircraft, so I am sure the airline will be keen to put the Airbus' to work on other routes!
Kyiv - Daily
Lviv - 3x Weekly
Odessa - 2x Weekly
St Petersburg - 4x Weekly
Moscow - Daily