This is nice, but I'm not sure getting this done would be worth the money (and shipping) that any company would be willing to charge for it.
You should wait the standard 1 year warranty out first (or extended warranty if you buy that), because if it fails in that time something was seriously wrong with it, and Sony will have to replace it.
If we look at the PS3, it was the original units that were hotter and even then most people didn't get the YLoD until 5+ years later. It was also the fact that the original units had more features which is why people wanted to fix them rather than buy a new console.
So if we take a look at the PS4, it's already running cooler than the PS3 and it is very unlikely that a new PS4 model will see a reduction in features. It's selling incredibly well, it's already cheaper than the competition, and it doesn't have any backwards compatibility this time so you won't lose anything functionality wise from a new model (I think years later they will drop the capacitive power buttons and probably add a manual flip open BluRay drive to make it even more cheaper, but that's about it).
Judging by this information, I'd say a thermal paste upgrade (along with a thorough inside dust cleaning) after your warranty plan expires should be enough to get you through the generation.
But all things said and done, the reduced power consumption and heat of the PS4 compared to the PS3 means overheating shouldn't be as bad a problem, or at least as widespread as it was with the original PS3 units.