[QUOTE=bornfreenowexpensive;5959856]
- Lots of them in eventing. 3/4 TB and 1/4 WB is even more desirable. [/QUOTE]
And I’ll throw some caution on here b/c the title of your thread asks if there is a market. Yes there is but the higher $ market, speaking to the eventing brought up, is exculsive to location, contacts and primarily when a horse is proven at a higher level ie competing recognized and above Prelim usually. Huge burden of expense, and the risks, to achieve this level. Babies, young stock, greenies not so much and the prices are much lower - unless – as noted you are playing at the top with recognized international proven bloodlines. And then again it helps to be a primary player in breeding. Folks with money want to say that they bought a horse from so and so, from such and such farm. The diamond in the rough standing in the nowhere backyard is not being ‘seen.’
The WB that looks like a TB and can gallop like a TB is desirable. Personally I bred 2 – better feet, balanced, more bone, sensitive like a TB, still have the TB heart, bold and willing, smart and want to please. But it is a genetic crapshoot. I count myself lucky, my DH says it was the stallion pick, he’s a H/J stallion, the mare had the sport TB blood and the mix worked well. I got an eventer and a hunter type out of the mix. And it’s 8 yrs later that we know this about them now that they’re out and working. Not for the faint hearted. 
As to a trend, yes I would say that the TB blood makes a horse a bit lighter on it’s feet and hopefully more catty. It may have taken awhile for the trendy folks to wake up again so the H/J market should follow. Your question really depends on where you want to go with it. And how you’re going to get there or if you’re just pondering a trend switch. Good luck.