Not sure it will be a good signing if people are already talking about LTIR before he’s even signed. To go on LTIR there has to actually be a serious injury not just an agreement by the parties. See Luongo as an example who retired without going on LTIR.
I don't think many of us are expecting Tanev to play well into his 40's.
They're more/less giving him a guaranteed contract into retirement to keep the AAV load and to limit his cap hit.