It appears that there are only 2 different areas of Bangladesh which still hosts tigers. These include the Sundarbans, an area of mangrove lying between India and Bangladesh and the Chittagong Hills Tract where photographic proof of a tiger has been taken. Unfortunately, though there are tigers in the Chittagong hills tract, it is unlikely going to be more than a few.
There is still some argument about how many tigers call the Sundarbans home. 114 tigers were identified, however as this survey only looked at about 16% of the forest it is reasonable to presume there are more. If all areas of the Sundarbans have similar densities of Tigers, we can estimate the whole population at about 700. Assuming this is prime habitat, the original number of 400-500 seems reasonable.
My judgement is that the tiger population has grown. I suspect that it has not doubled, but it has increased. I suspect that there is still significant poaching, but with continued efforts these tigers could recover.