Although the long term strategy for the airline was intended to be a 737-800 / 787 only fleet, approximately x10 757's will remain with TOM for the mid-term and for at least the next 5-6 years; with the possibility of some lease extensions too.
This is simply because there isn't an aircarft currently on the market that can fill the gap the 757 would leave with regards to payload and endurance in the short/mid haul market.
Much of what has been said about reduced capacity requirements and hence the 737's is correct. However, the airline have conceded that the niche the 757 fills on certain routes from certain airports can't ideally be filled by the 738, and therefore a fleet evaluation will be required in the near future to see if there is a potential replacement for the 757's towards the end of the decade, or whether they will live with the 737/787 only fleet as best they can going forward.