Porting Access To SQL Down The Line

I have started a new site using a CMS which can be either Access or MS SQL. For ease of install and cost factors the site is currently running as an Access dbase driven site. If traffic numbers and content grow and Access dbase blows out to, lets say 500meg will I see a major degradation in performance and will it be possible at a later data to somehow export the Access dbase data into MS SQL dbase format. I'm assuming I'd have to engage a fairly competent developer but before I get into the trap of growing a large site, I'd like confirmation that I'd be able to extract all of the data and get it into a more robust solution as and when required. phew!