My view remains 'more = better' (when it comes to bike shops).
BUT for them all to survive/thrive they need customers - more people to buy more stuff.
Whether that 'works' depends on lots of things -
state of the economy - whether people have money to spend on stuff and/or 'downsizing' from car to bike.
how much Edinburgh becomes the 'world class cycling city' (as 'promised').
how other shops 'react' to Evans.
Evans isn't just another bike shop it's a brand - better than Halfords and a lot bigger than EBC.
Of course Evans will be competing with all the other shops and they with Evans - mostly by being different in the way Edinburgh bike shops already are.
Bike shops (wherever) are people businesses. In the past they were (sometimes) run by grumpy men in brown overalls or ex-racers who didn't seem to like non-racers as customers.
Now (the good ones) work hard at customer relations. Of course there will always be people who prefer the anonymity of Halfords or 'favour' no particular shop.
In the bigger scheme of things bike shops aren't competing against each other. They compete with other shops that sell shiny stuff. They compete with an overwhelmingly car-centric world, even in Edinburgh...
I hope Evans sell lots of bikes - especially to people who didn't previously have one, and so add to the number of people cycling in Edinburgh, which must be a good thing.