Mark my words. The biggest sporting event of the year (next to the World Cup) will happen. The only question is how much posturing over drug testing we'll have to endure until contracts are signed. Both parties have to walk a fine PR line here. Pacquiao has to agree to more stringent testing so as not to be perceived as a cheater while Mayweather has to give a little on his demands for full Olympic-style testing to avoid looking like he's trying to dodge his toughest challenge yet.
In the end, though, they'll get it done. There's too much upside for both fighters in terms of money (not only for this fight but also for a possible rematch) and prestige (it will be the most watched fight in the sport's history).
Who will win? That's a debate for another day.