Soon your old analog TV will be obsolete. If you don't subscribe to cable or satellite TV and to get over the air TV at all you will need to get a converter box. The neat thing is that with government rebates you can get them for almost free. Once you have them it won't make your old analog TV high definition but you will get a clearer picture and you can get many more years of use out of it without having to get a new TV. The reason that analog TV is going the way of the telegraph is because it is a very inefficient use of the radio spectrum. The FCC realized, pressed by demand from the business sector, that it could sell the frequencies that are currently being used by analog TV to the highest bidder. These channels will be reallocated for services like mobile internet, new cell phone channels, etc. This will mean more mobile communication choices for us as new product are able to be developed to use these frequencies.
You can expect this kind of sweeping takeover of bandwidth to be more and more common with a growing threat to Amateur or "Ham" radio frequencies that have been fiercely guarded in the past but are coveted by the mobile electronics industry.
The site below has links to the US government rebate program.
http://www.ehelpfultips.com/how_to_convert_your_old_tv_to_di.htm