There's a chance Bangladesh might draw a Test, still two days to go but my rule of thumb is if the first two innings aren't completed by the end of day 3 then it could well be heading for a draw. Sri Lanka will need to wrap the Bangles up inside two sessions, they do have a sizeable lead, but if it is reduced to around the follow on mark of 200 then it could be hard to force a win where 800+ runs have been scored.
Bangladesh could of course collapse, Sri Lanka don't look a shadow of the side they were not so long ago