The question is a two-parter.
1) What happens to the keys in your inventory?
The wiki states:
During some special events, specialized keys are made available. These keys can be used with specifically associated series of crates, which regular keys cannot open. Remaining special keys, at the end of promotions, are transformed into regular keys.
Is this true? Does this mean I have to buy new keys? This sounds a bit strange, especially if I still have some weapon cases remaining.
2) What happens to keys in general (in the shop)?
Will I still be able to buy keys from the store after the promotion ends? If not and the above is true, that would render any remaining weapon cases i have left at the time useless.
I still see a lot of older keys in the store but not all of them and I can't find any info on what will happen with left-over weapon cases / keys after the promotion ends.