i was wondering if it would even be worth getting a blue ray player with only 720p Tv?
YES.
1. Blu-Ray has won the high definition war, and it's going to be around for quite a while. I see no reason why it won't have the same lifespan that standard DVD's did. A Blu-Ray player is something you can confidently invest in now, without having to worry about it being obsolete in a year. Even if a new technology comes along, you're safe until manufacturers start making panels with resolutions greater than 1920x1080 - and that's not going to happen for a long time. If you buy a player now, you'll already have that piece of equipment in place if and when you upgrade your TV.
2. I consider myself a videophile, and the truth is, on most material you wouldn't notice a big difference between 720p and 1080p unless you had two identical TV's side by side, showing the same thing but at the different resolutions. The size of the panel also contributes to the noticeable difference between the resolutions. Under 40", you won't see a whole hell of a lot of difference, even under scrutiny. To really reap the benefits of 1080p, you need a larger display.
3. A Blu-Ray player will upconvert your standard definition DVD's to whatever resolution your TV is capable of. You can't magically transform standard definition material into high definition, but players that upscale do improve the quality quite a bit.
4. Blu-Ray players have HDMI inputs, MUCH better than analog component, S-video, or composite video cables. HDMI offers quite a bit of improvement in sharpness and color over component cables. Even more so with HDMI v1.3.
5. I've experimented with a 40" Sony TV (mine), two 52" Sony TV's (one of which is mine), and a 52" Samsung TV - all of which are native 1080p, but I've tested them all at 720p. You have my word that a Blu Ray disc being displayed at 720p is going to look
outstanding. No, not as good as 1080p, but you're still looking at 921,600 pixels. And an optical Blu-Ray disc, fed through a digital HDMI cable, is going to look tremendously better than any 720p television broadcast.
I could go on, but you get the idea.