Warning, possible endless babble alert with poor English/I am very tired, skip if you want..! This trade has been on again/off again for basically the whole offseason, but seems to have gained momentum in the past 48 hours or so again. One of the main reasons I had not dismissed further trades since the Ray Allen trade was we hadn't signed any of our draft picks from this past draft yet..
The negative/positive argument seems to be based on 'mortgaging the future' to 'dude, its KG, you do what you can to get him'. A lot of fans get really attached to their young players thinking they will be the next MJ, Lebron, Shaq etc and are reluctant to trade on the 'what if player x becomes a superstar, then we will look daft in years to come etc' premise, and I think this is the case with many Celtics fans and Al Jeff and to some extent Rondo. Both players have the potential to be v good/ borderline allstars imho but this would take time, time which the Celtics probably don't have with Pierce and Allen now. With the trade for Ray Allen it was probably the biggest indication that the organisation were willing to make a move for 'winning now' rather than 'develop for the future' (they could have just been trying to appease PP though J) .
To get KG without giving up PP or Allen just seems the safer route for me. Sure, Al Jeff broke out a bit last year, but the bottom line was it on was a lottery team. I still think he will be a very good player, but whether he gets to a KG or anywhere near a KG type standard player is a burning question. There is also Ratliffs massive expiring contract which will be very valuable and sought after in trade talks. Then you have some good 'potential players' such as Rondo and Green, but then there is the risk of turning into the LA Clippers of the 1990's, decent/good young players/draft picks but no real blue chips and the rebuilding process will not end up being worth it.
Bottom line I say the Celtics should go for it. Screw rebuilding if you can have KG, PP and Ray Allen on the same team, this team on paper would be great in the east and would gain massive attention throughout the league. MJ won his first title around the age of 28 I think, no reason why a team with those 3 superstars on it couldn't seriously contend for the Championship, or at the least, be better than Chicago.