I planned to change my A1 for and S3 early next year but ordering Oct / Nov time this year. I had even done a spreadsheet working out my finance balance and expected trade in for my A1, how much I'd save for deposit etc.
But in the end I was coming on here every day and getting myself quite worked up about it (saddo). So few weeks ago I was sat at my desk at work and thought there was no harm in asking the question about sorting a deal now. So just drove down the dealer. Was quite surprised I could do a deal and hey presto the next day it was ordered. Just got to wait until May now.....
In respect of the yearly model changes - don't expect much so new after launch. I think the first major changes to the A1 spec came in 2013 MY (two years after launch). Major things that changed was seat stitching went white to silver, they deleted the roof aerial and I think the DIS went to colour. 2012 model year before (mine) the only things amended was some protection film around the boot opening stoppers and a steering wheel paddles became a no cost option. Nothing spectacular.
Guess the longer you leave it the closer you will get to a face lift which will probably be 2016 / 2017 (four years). Looks like from the A1 face lift pics that they are moving over to A3 style grill and DRLs. Think I read somewhere they are uniforming the DRL's across the range like BMW angel eyes.