SSD module connector backwards compatible?

You mention that the module has a different connector. Unfortunately, only the ground-plate side is shown of both. There is a picture of the front side of the connector of the new SSD. It would seem that it has about as much of a ground plate on the left and right as the connector is wider.

So I wonder that while obviously the new SSDs won't fit in the old computers, if the older SSDs fit in the new computer, if one's willing to have worse grounding with whatever problems that may create, or if the actual signal leads are also differently spaced and assigned.

Key thing here: the biggest issue with last years is that they only have up to 4GB RAM which is a real bottleneck. Some people bought an Aurora 480GB SSD from OWC, and it would be an easy upgrade to the new machine if one could get a cheap 128GB version model, and stick the old drive in there. On the other hand, having to buy another 500GB drive makes this an expensive proposition...