I think the biggest thing about the gamepass is the price where MS are practically giving it away. They've used this gen to prototype it and build its reputation similar to what Sony did last gen with free online.
The start of next gen I think the silly gamepass price will disappear with either a tiered gamepass or one with a more realistic cost. This will then change things massively to gamepass adoption and retention.
Secondly, the studios that MS has bought, I would say only two are amazing great studios with reviews and sales to back them, Playground and Obsidian. The rest, including NT, are more padding than amazing acquisitions.
Sonys shift in strategy and head start with their big exclusives will make a difference. Instead of sequels at the end of the gen, we will probably see them release gradually early next gen, bridging that slow first 18 months. GOW sequel, Horizon, Spidey, GT, Killzone, Infamous maybe even smaller games like R&C, Knack and remasters thrown in for good measure.
Since Sony already has their pricing for PSNow sorted, it won't come as a big hit to their player base, so it won't affect retention or adoption as much, in fact during the first 18 months we might even see a rise in sales to bridge those 18 months.
XCloud as great as it theoretically is, we are yet to see a game fully take advantage and show it being plausible, but it is nothing Sony can't do or any other dev for that matter.
Ultimately I think Lockhart will play a greater role depending on the price. If they price it right, with decent specs, it will be what will bring in higher xbox sales, and that's if Sony doesn't create a digital only PS5. However, if rumours are true and Lockhart is speced around the ps4pro, and will cost around £300 (assuming Anaconda might be £500), then my question is why not just buy a Xbox1X?!
I think MS are behind (if they are), due to low console sales this gen. If the cost of orders is dependent on quantity you order, then sony won't have an issue securing a good deal as history has proven they can shift consoles. MS on the other hand got lucky one gen but have struggled for every single other gen. If they have to make tough decisions on orders (why they may have brought Lockhart back to increase sales of parts), this may be the reason why they are stalling.