Learning a second language has been shown to reduce to risk of dementia, so perhaps teaching Welsh in primary through to high school isn't a bad idea. I had to do GCSEs in a minimum of 2 foreign languages (children with dyslexia/disabilities could choose to only do one MFL).
Although I am not Welsh, I have been brought up bilingual, and hence have had a better understanding and appreciation of that culture. Being able to speak two languages has encouraged me to speak, and to continue to speak, a third language as it's easier to learn if you already speak more than one language. I think this enriches my life as I'm able to appreciate things like movies/arts in that language, even when the majority of the people I speak in a foreign language speak English too.