Actually i think we have a very good idea of what will be available in terms of long-range widebodies in a decade - A350, B77X, B787. If we want to go "fringe", the Il-96-400 may still be available for sale and China might have the C929 flying by then (although neither would be seriously considered by an airline like AC). The 350 and 787 will likely have a newer engine a decade from now but the basic airframe will still be around just as is the case with the 737/320 series.

There is zero talk about a new clean sheet design widebody for availability within the next decade.

And yet plenty of airlines chose the EMB175 over the CRJ705 despite the latter's better operating economics and speed (albeit at a higher price charged by BBD). They bought the E-jet because it feels more like a "mainline" aircraft whereas the CRJ always felt like an RJ despite BBD's attempts to dress it up a bit.