Yes, Solange Knowles' wedding will have a big influence on wedding fashion. Society today like to follow in the footsteps of celebrities, and I expect this to be no different. Solange Knowles' wedding style will be the next in-thing until another celebrity does something different for society to pick up and run with.
I think it might have minor influence on upcoming wedding fashion, in that there will definitely be a market of people who are particularly obsessed with the Knowles girls who will want to emulate what they see. However, if it was her sister Beyonce's wedding fashion instead of Solange's, I think the level and range of influence would be lightyears different. Solange's recognition only really comes from her relation to her famous sister, so her fanbase isn't as widespread as to affect an entire genre of fashion.
No, there will be no impact on wedding fashion as a result of Solange Knowles' wedding. Though she wore a very contemporary jumpsuit instead of a traditional wedding gown, it's very unlikely to make any impact whatsoever on the typical wedding dress sensibility. Her outfit was not really appropriate for a traditional wedding and was overly sensual.
Even though Solange Knowle's is related to the world famous Beyonce, her wedding won't have a big influence on wedding fashion. Simply being related to someone famous doesn't automatically qualify that person to influence fashion or any pop culture style. There will quickly be another wedding with a much more famous person that will overshadow Solange Knowle's nuptials.