Type freeze only applies to new pilots joining the Company and is for 3 years from the date of joining the Thomson seniority list. Other than that no freezes, and there have been many cases of pilots "flip flopping" from one type to another and back again to satisfy seasonal imbalances. The MAX is scheduled to begin arriving in 2018 I believe, gradually replacing the 757 and then NG fleets.
There is also the (rather tortuous) introduction of "One Aviation" within the group airlines across Europe. This has suffered delays, but already pilots from the UK fly services from Scandinavia regularly on long haul routes, and there are winter detachments to Sunwing in Canada flying mainly down to the Caribbean and Mexico on the 737. This has been a source of continued employment year round for the recent PPY joiners.