Johnson's comments today about it being too early to say if lockdown will be lifted in Spring, and that "we'll see how we're doing at the 15th Feb review" I think confirms that nothing has changed regarding the criteria since he announced the lockdown on the 4th. I take this as positive, as some in the media have been spinning stories recently about the goalposts shifting and painting a bleaker outlook.
If things are going as well as realistically hoped come this review, the 'if' having to be stressed, then I'm going for schools reopening on 1st March (government today said schools will be given 2 weeks notice following announcement of reopening) and a return to the tier system on 8th March. It'll be tiers 3 or 4 everywhere to start with, the decision on either tier 3 or 4 for an area depending on how well it is doing. By the 8th March we'll have hopefully passed the 20 million mark for first dose vaccinations, which should start making a big difference for hospitals, that'll be the hope.
Wouldn't surprise me if things then stay as they are for another 4 weeks which will take us up to the Easter weekend, with a review the week before. At this point I think they'll then look to start placing areas back into tier 2 and the reopening of hospitality (possibly using the original tier 2 and not having this substantial meal rule), again subject to how well things are going.