Negative spin? The editorialising of it is reasonably nuanced, even going so far as to point out that customers “[might not] have to trade in [their] older Model S or Model X vehicle when taking this offer”, and calling the offer ‘interesting’.

Really hard to see this as anything other than at worst neutral.

We can also assume that Tesla will remove the free unlimited supercharging from these models and then re-sell them on he market.

If I wanted to trade in my Model S with unlimited supercharging, I'd sell it on the used market and use that as a premium to get more for it.