The generic PC could have been getting much cheaper and perhaps specialized, but the complicated interplay between the dominating operating system and consumer market social aspects lead to the development which simply happened. But somehow everybody in science was happy.
Without going into details of the "wars" this time, the direction of this unusual evolution where one species PC nearly extinguished all other forms has changed rather abruptly by one computer scientist who started to realize a dream about "one laptop per child" - OLPC. The OLPC has shown to many what some new from before: you can have use for other devices than the omnipresent PC.
In a relatively short period then followed notebooks inspired by OLPC. But here the empire struck back and cannibalized the notebooks making them into "inexpensive laptop PC". The next step of the hero engineers was to invent a smartbook, a netbook which was so smart that it did not use the processor which could work through windows and spread the Word. That phase never started, because before that we have got iPad which the computer journalist now see as the sole future of computing. So soon there will be affordable PCs, only iPads or other Pads.
What has all this to do with science?
Historically, the development of computing devices has been stimulated by the needs of science and most advanced technology, often unfortunately for not quite peaceful purposes, but that was mainly in the beginning. In the recent time the development seems to be dominated by consumer electronics, devices which might be very useful for science and education - but see the development sketched above.
I did not discuss this yet but a quick look at popular computer journals will show you that the games and video are the driving elements now. So what will happen with all the labs in 5 years time when the only computers available for reasonable price might be sort of iPads, sealed and without input ports? I sort of like the iPads, but they are going the wrong way, just opposite what that company used to do before - make people smarter.
iPads are unfortunately mainly designed with a different aim. One scientist played an important part in this computing soap opera - the originator of OLPC. Perhaps scientists should somehow rethink their relation and needs and concepts with respect to computing. The nearly 30 years of PC produced also lots of myths and ignorance in this filed too, as in others related to science.
And now we hear that computers are smarter than best humans in a marvelous game of inverting the answers into questions (keyword: Watson). But those are not PCs.