edwyun, you bring up a good point. If the repositioning and the cable changes were concurrent, then there is convolution as to the contribution of the cables and the repositioning. However, if they were separate events, then the characteristics of each would be obvious.
This is one of the best questions I have encountered here in a long time. I have always considered the positioning of the speakers independently of the cables I use, however, there is no necessity of that. If a person wished to reconsider their positioning of speakers due to cable change, they certainly can, and may discover a preferable positioning.
I can envision certain circumstances where cable changes could potentially introduce the question of speaker positioning. i.e. some cables carry such strong low end emphasis that if speakers were placed near a boundary, or were in a highly reflective environment such as glass wall, then repositioning might be encouraged. It may also be potentially necessary to remove some treatment, the reverse effect due to cabling changes.
Imo most of the critical aspects of performance due to positioning are not significantly enhanced or diminished due to cable changes. Cables do influence dynamics, tonality and definition, but cannot resolve problems due to poor placement or vastly improve good placement. Once you move your speakers you have lost your reference. Not that it's a sin; do whatever you wish in terms of placement with new cables! Explore! Experiment! That's half the fun!
About a year ago I decided to revisit entirely my positioning of speakers. I moved the subwoofers fore, pushed back the mains, basically reconsidered everything and the result is wonderful! I should have experimented more a long time ago. Thankfully I was not forever bound by convention, and now have a much better experience.
So, I say have at it! If you feel the urge to reposition them, do it! No one can tell you that you are going about it wrong. :)