I did some quick searches, but Merckx doesn't seem to list their head tube angles. In spite of that, let's make some guesses and run the numbers. A good online calculator and picture is here if you want to continue playing with the numbers: http://www.kreuzotter.de/english/elenk.htm
Merckx does list the head tube angle of the carbon GX2 as 72.5 deg on a 57 bike. This gives a trail of 60 mm with a 700x23 tire. Most people think the sweet spot for trail is 55-60 mm so this is on the stable end of the normal range. Increasing the rake to 45 mm decreases the trail to 58 mm. This is a very small change and is still in the normal area, and may be described as "nuetral" by many people. Good luck finding a 47 mm rake fork, but if you did the trail would decrease to 56 mm, which could be described as "quick", but still within the normal range. A 41 mm rake would increase the trail to 62 mm, which is stable, verging on over-stable.
These are relatively small changes and can be thought of as fine-tuning rather than radically altering the handling. Some extreme examples, to give you an idea of possible trail ranges, include motor pace bikes and my hacked Trek Y-Foil.
Bike used in motor paced racing have forks that look like they are turned backwards. In truth, they are designed this way in order to give them a lot of trail (70+ mm) so that they are very stable at high speed. My Y-foil, on the other hand, had something like 35mm of trail becuase the fork I used, an Easton EC90, was a full inch shorter than the original fork. This lowered the front end and increased the head tube angle to more than 76 deg. The bike was very rideable and very eager to turn. I had to pedal very smoothly when riding no-hands, but it soon became second nature. I even completed a number of double centuries on it.