For what it's worth, when Epcot first opened and throughout the following decade there were just as many Scottish and Welsh goods. I can tell you that my family bought more than our share of scottish wool sweaters and tartan scarves, there used to be a very chic shop for that sort of thing. I also clearly remember being able to buy all sorts of souvenir goods sporting the Welsh dragon.
Sadly, as happened with many of the World Showcase pavilions over the years Disney lost sponsorships for the goods and products that made the Epcot shopping experience unique. Today guests will find the same "Got Wine?" shirt in Canada, France, and Germany - all made in China. It's truly frustrating. While several companies have built their American reputations and distributor ships on the back of that original Disney contract, many of them also failed after the contracts lapsed.
The amount of merchandise that remains will likely be subject to whatever contracts that Disney has in place with the companies in the first place. However as those contracts come up for renewal Disney will have to make a choice as to if Scotland will remain. For the record, it will not be pretty if I can't get my shortbread.