Dragonstar?
Or Shadowrun or Unearthed Arcana without the real-world implications?
Not only has it been done, there are actually d20 supplements that will help you do the precise thing you're talking about.
Now, thinking specifically of FR, I don't think tacking 1,000 years onto it would get you Traveler or Star*Drive tech levels (or Dragonstar, for that matter). Going by real-world progression, you'd probably be looking at something nearer-future, more 2001 than Star Trek, more Tales of Known Space than Mote In God's Eye, more Shadowrun than Dragonstar.
Realistically, such a high-magic setting is going to advance much more slowly in other ways, because the rich and powerful already have access to most anything technology could deliver. Elminster doesn't need a ray gun because he is his own ray gun. That's not to say innovation won't occur; the priests of Gond already invent new tech by religious directive, and even those ubermages would likely fiddle with it from time to time, just to alleviate the passing of eons. However, the new tech would move forward in fits and starts, and it would likely not see widespread use. It wouldn't be unusual to stumble across 'Elminster's Magnificently Mundane Flight Apparatus' (an ornithopter or even a working jet plane) in 1,000 years - but you wouldn't see the Cormyr Royal Air Corps taking on Zhentil Aerospace, nor Drizzt's descendents popping on a jet liner while dual-wielding the laser pistols Blazingdeath and Sparkle.
More interesting scenarios for a tech-magic hybrid, IMO, are what you see in some of the Final Fantasy worlds.
In FF6 (steampunk tech level) and FF7 (cyberpunk tech level), the world basically advanced *without* magic, explaining where the tech came from, until someone in the already technological society *discovered* the use of magic. In FF6, the discoverers used it to advance from steampunk to pseudo-cyberpunk and tried to take over the world; in FF7, they used it as a power source for their existing technology, by and large using it for economic rather than military purposes.
In FF12, magic was used for centuries to *power* what we would normally think of as technological advancements. So you get the sleek looking modern technology, but its development in a magical world makes sense.
Keep in mind that most of the FFs are *much* lower-magic settings than a typical D&D setting, which is part of why the magic and tech hybrid works. A humanoid with innate magical powers in FF6 or FF7 is vanishingly rare - a focal point for the story even if not exceptionally powerful. A 6th level D&D sorcerer's existence would be a world-shaking event; a wizard, simply impossible. It makes sense to use magic to power a vehicle in FF12, because a spell cast by the world's most powerful human wizard is vastly weaker than what the vehicle can do with the same amount of power. This doesn't apply to artifacts or monsters, of course.
Shadowrun works largely for the same reason. Its tech developed in the 'real world,' sans magic, for all of our recorded history. It continues to develop in the awakened world because magic is not nearly as safe, widespread or reliable as in D&D. While a dragon is the president of a major arms corporation, he doesn't pioneer the development of new guns for his own use - he does it to increase his hoard, knowing that all the guns in the world won't be able to scratch him.
In Urban Arcana, magic at least starts out hidden from the wider world. Since it is safe, reliable D&D magic, it would probably supplant technology over time if it was revealed and popularized. Urban Arcana's Earth is more likely to look like Abeir-Toril in 1,000 years than Abeir-Toril is to look like Urban Arcana's Earth.
Or, you could handwave the development of the tech and get down to the important bits: dragons in rocket ships!
