I question how good an investment this will be.
Everyone knows how much the old one went up, and will be buying for just that reason.
Still doesn't change the fact that in 10 years, buying second hand will be the only way to get it. Granted, I wouldn't expect another bubble of $5000 Falcons, but I can imagine getting $3000 for an unopened one (years down the line, obviously) without much fuss.
The only thing that might affect the price is the knowledge that Lego is beginning to revise and update older UCS sets. They did it with the Snowspeeder and they're doing it again here. So if you're not married to this particular UCS Falcon, some prospective buyers might just want to wait another 10-15 years for them to make a new version.