Would it be an upgrade?
Absolutely!
Would it be worth it?
This is entirely in your own personal arena. Don't get me wrong, but asking others to justify your purchase isn't the way to go. There's no question that the older Sony doesn't hold up against the 1080, or the 1080UB, but the $3,000 outlay for a projector, and likely a mount, is not something I could just say 'Go for it!' to if you really can't afford it.
This is a luxury item, and you have soemthing that works nicely currently, so you really are going to realize what may be a 20% or so jump in overall, visual, performance. That will be a resolution and contrast jump.
HDMI 1.3 really matters very little in video, but matters far more for audio, which might be a better thing to upgrade.
But, if you have the cash, and it is disposable money, and you are ready to make the upgrade, then you certainly will get one with this projector.
Whether it is worth it or not is entirely up to you though.