2) I'm also scared that some new technology will come out making 6GB/S outdated. Is anything coming soon?
With technology, there is always something better coming...nature of the beast.
I'd definitely recommend getting an SSD..at least for the operating system drive. However, OCZ doesn't have a good reputation for quality. I got an OCZ drive when SSDs first starting coming out and it was DOA. Replacement has worked like a charm though but based on what I've read on forums, a lot of people have had issues with SSDs from OCZ.
I'd get one from Intel, Samsung, Crucial, or SanDisk. I was able to pick up a 128 GB Samsung 830 for $84.99 on newegg for my desktop and a 128 GB SanDisk Extreme SSD for $79.99 on amazon for my laptop. Just have to keep an eye out for the deals, which seem to come on a regular basis.
120/128 GB SSDs seem plenty fast to me and in real world day to day performance I'd be surprised if he would notice a difference, especially since I think the sata 2 connector would be his bottleneck.
jbl, the one you linked is a good option if you don't want to wait for a sale. (review: http://thessdreview.com/our-reviews/corsair-force-serie...). In the past couple weeks, there have been comparable SSDs on sale for $10-20 less. The only caveat is not knowing when the next sale will be.
No matter what SSD you buy you will see a performance boost, the OCZ vertex 4 should do you just fine, once you have it installed have look for (or better still have a quick read before) "Sean's Windows 7 Install & Optimization Guide for SSDs & HDDs" as a good guide to setting up your SSD.
If you can afford to buy an SSD that is larger than 120Gb it may be worth your while spending a little more.