The way I see it, if (and I'm not saying they are, just if) the Colts are indeed tanking, so what; let them.
First of all there is no guarantee that Luck is going to be a great NFL player, and there is certainly no guarantee that he will turn the franchise around.
Losing breeds a losing attitude in the locker room, and that cannot be turned on and off like a light switch. And losing affects the fan base too; ticket sales are bound to drop, and with less than anticipated revenues budgets - including the budgets for player salaries, coaches salaries, and scouting - could be cut.
Indianapolis has never been much of a player in the free agent market, and a team coming off an 0-16 or 1-15 record in a relatively small city is not going to help recruit free agents. That means the Colts are going to have to outbid other teams for available players - something they've never done, except for players already on their roster - in order to sign them.
If they do try to get better quickly, then after over paying for a few players they'll be bumping up against their budget, and have to fill out the roster with less talented players making rookie minimum salaries.
If they don't look to improve through free agency then hat means they'll have to rebuild slowly through the draft, but as we have seen the last few years they haven't been drafting very well because apparently many of the scouts and personnel people that were there when they were the NFL model on how to succeed in the draft are now gone.
Colts Daily Links: Luck backlash, Chris Polian's inheritance, NFL history | The Indianapolis Star | indystar.com
So as far as I'm concerned, let them tank if that's what they want to do. Besides, I'd rather the Colts have the top pick than a team in the division that the Pats face twice a year: the Miami Dolphins.