Thanks to The Flash, a major villain from Batman Beyond officially exists in the Arrowverse. Ever since Arrow debuted, the franchise has always enjoyed dropping Easter eggs and making references to other DC characters and storylines. In most cases, whenever one of the Arrowverse shows name-drops something from the DC Universe, it does get a pay-off down the line. There have also been instances where certain DC Easter eggs don't lead to anything; however, even those references help flesh out the Arrowverse and make it feel bigger.
The groundbreaking 150th episode of The Flash was full of Easter eggs. The Flash occasionally expands the Arrowverse's past and future, which is a great opportunity to reference other DC properties. Titled "Heart of the Matter, Part 1," episode 150 showed Iris West-Allen and Barry's kids Nora and Bart, a.k.a. XS and Impulse in 2049, giving viewers a look at Central City in the future. After temporarily stopping Godspeed, XS and Impulse had a brief heated discussion, which is where the Batman Beyond connection comes into play.
Across the street from where Bart and Nora were standing is a sign that says "Powers Technology." While it may not mean much to mainstream viewers, that company belongs to a very famous DC villain named Derek Powers, a.k.a. Blight. Powers was the first main antagonist for the Batman Beyond animated series during season 1. In Batman Beyond, Powers was a corrupted businessman who had merged companies with Bruce Wayne in the future; however, after getting exposed to a dangerous nerve gas, Powers put himself through nuclear radiation treatment. While it made his skin toxic, thus giving Powers his famous green look, he developed radioactive abilities and became Blight.
While Blight doesn't show up in the flesh, The Flash is the first DC live-action property ever to reference Powers and his company. Interestingly, Arrowverse's Batman Beyond Easter egg specifically seeded Powers Technology in the future timeline, not the present. Since the Arrowverse can't use Bruce regularly as Batman, if they ever introduce Terry McGinnis, they already have Blight set up as a major villain since Powers Technology exists in 2049. Thanks to The Flash, the Arrowverse could use the Easter egg as a jumping point for a potential Batman Beyond live-action show. If The CW can't do Batman Beyond, Blight could be a possible villain in a potential Arrowverse spinoff for Impulse and XS.
Had Green Arrow and the Canaries happened, it would have allowed the Arrowverse to have a weekly series that takes place in the future. That is something the franchise is currently lacking on The CW slate. It would genuinely be intriguing to see an Arrowverse spinoff that shows Earth-Prime 20-30 years from now. Whether it be a Batman Beyond series or an Impulse/XS spinoff, the Blight Easter egg on The Flash makes a good case for why the Arrowverse should explore the future in a bigger capacity.