It is a fair point, I certainly don't think they would do a Sheff Wed, although would not have it off the table, but there is a chance that they may not find it all that easy.
Most likely you are right, just think that the squad overhaul that would be needed is going to put that guarantee of straight back under pressure.
It would be interesting to see how many players stayed with Newcastle, and what the squad overhaul was like, compared to what is likely under Spurs. Different types of mismanagement? Not buying good enough players while in the Prem, so keeping the core squad but them being good enough for the Championship and only needing to add a bit more 2nd tier quality to a few areas. Compared to buying good enough players, that won't want to stay in the Championship, but other things going wrong.
It will certainly be an interesting watch, if they do go down. Maybe another Netflix jinx like with Sunderland

.