Example, you currently have a 60 GH/s rig and you want to get 300 GH/s or your current one hashes to your liking but it uses too much power. So you mail it in and they upgrade it and you save having to buy a whole new piece of equipment. Or will this be a job for my friendly local electrical engineer?
KNC had some earlier upgrades for some of their Saturn model, but then no longer added those options to other models. I think it all comes down to power needed, ie you need to add another power supply. At that point, the simplicity of the "upgrade" is lost. The blade erupters were probably the cost thing to "upgrades" by just adding boards.
ASICMiner Blades:
https://bitcointalk.org/?topic=205369.0