Multi MB save issue has not been fixed, it has been moved from the previous 6 MB threshold to 11 - 12 MB threshold now. That means that usually the symptoms only start appearing after 100+ hours of gaming (depending on how much you explored the game, how many items you have stored, etc.). After the game becomes "cluttered" in random point data stored in the save file, it becomes slower to read thus the lag.
It's a memory issue that has not and will not be adressed for the PS3 version unfortunately (Fallout New Vegas suffered from a similar bug too), but recent patches have made sure that you can at least get a full playthrough decently.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
