Russia would be wise to take a rather relaxed view on Debaltsevo, let the Ukraine army
stay there and then negotiate the issue after the cease-fire is really holding. The town is not that strategic to the rebels unless they want to control the rail line. They should be more concerned about getting peace if peace is what they want.
If the rebels make a huge deal out of the presence of those troops and do not permit a negotiated and orderly withdrawal or exchange or peaceful resolution of the situation, they are demonstrating a lack of desire to resolve issues peacefully.
The presence of those Ukraine troops in that location is more an excuse for continuing to fight for the Russian-supported separatists than it is a real issue.
The situation will resolve itself quickly because the Russian-supported rebels are basically in control of that area. They can afford to surround the 5,000 troops and wait it out patiently until the situation is resolved through negotiation.
The world will be watching this. It will be a way for Putin to demonstrate whether he wants war or peace. If he relaxes about the presence of the Ukraine troops there, it is a sign he wants peace. If he makes a big deal about getting them out, it is a sign he wants war.