If you sear it and allow to sit at room temp it will weep a lot of the juices.....pork tenderloin cooks so quickly, there is no reason to do much ahead. I rub with a seasoning, often dijon mustard and a bit of garlic powder and sear on an oven proof skillet, about 5 minutes on a side, then slide it oi nto a heated 375 oven for about 20 minutes, when the temp reaches about 140. You can then tent it with foil and keep warm for easily 30 minutes if you wish.
Or you can coat it with something dark....like balsamic vinegar or even terayaki sauce and pop it into a 357 oven for 30 minutes. Soy-Vey makes some delicious dark marinades that brown the meat very nicely.

I don't know anything about cooking pork (I defer to Linda), but restaurants sear steaks ahead of time and then finish them to order. That's one of the ways they get the dinner out so fast. Maybe if you sear it very hot and very fast, then chill right away to stop the cooking? I don't know what that would do to the fat, though I'm guessing tenderloin is pretty lean. Summary: There might be a way to make it work, but I don't know what it is. :) Good luck!

I only sear for "looks" or to develop a base for gravy or sauce. If your recipe doesn't require a sauce from the meat, I'd skip searing and just roast it.

Actually restaurants cook the steak ahead of time and sear at the last minute...often sous vide.
Pork and beef cook prettywell the same, but these days pork is bred so lean it's almost like white meat chicken. But a pork tenderloin is such a little skinny piece of meat it doesn't take long to cook.

The biggest danger is overcooking it and drying it out.

If you want to try something different, wrap it in prosciutto, brown that, chill it, make a duxelle of mushrooms, or get some pate, take a sheet of puff pastry, spread the mushrooms or pate in the middle, put the pork on top and roll up into a Wellington. Serve with a mushroom gravy or Madeira sauce. Then, it just sits in the oven while you entertain your guests and less worry of drying out.

Thanks for all the suggestions -- I did a trial run last night -- a pork, apples, and onion, recipe. Delicious and port was perfectly cooked in 20 minutes. But more last minute work and worries than I like for a dinner party, so I will find something else.