What would be the point? If we're being cynical, it's largely a marketing play—higher numbers suggest better performance, and since NVIDIA already released a standard GeForce GTX 950 to replace its GeForce GTX 750 Ti, why not release a GeForce GTX 950 LP/SE to replace its regular GeForce GTX 750 as well?
Be that as it may, the GTX 950 LP/SE isn't a simple rebadge of an older card. Based on Maxwell 2.0, it's a more power efficient card compared to the GTX 950 released last year, and offers faster performance compared to the GTX 750 released two years ago.
Bearing in mind that nothing is yet official, the GTX 950 LP/SE (GM206 GPU) is said to feature 640 CUDA cores and 40 texture units, up from 512 and 32, respectively, on the GTX 750, and 16 ROPs (same as the GTX 750).
If we're still comparing to the Maxwell 1.0-based GTX 750, the GTX 950 LP/SE will also feature twice as much GDDR5 memory at 2GB, while maintaining a 128-bit memory bus. Clockspeeds have yet to be determined, though it's expected that both the GPU and memory will run faster, resulting in at least 104GB/s of memory bandwidth (the GTX 750 offers 80GB/s).
The key here will be pricing. After rebate, you can find a GeForce GTX 950 for around $120, and not much more before rebate.