Well, possibly, but Mana, YFood, Feed and Saturo are all RTD products available in the EU. Online ordering seems to be a healthy competitive scene, and the Plenny Drink will only join this crowd.
What Soylent has done in the U.S. is to aggressively move into “bricks and mortar” sales, getting agreements with some nation-wide retail grocery chains. This has definitely put it in a dominant position with respect to retail. Because of the difficulty of obtaining “shelf space”, it is very unlikely another meal replacement drink could now appear in those stores(*).
But online is a separate world. I expect that the Plenny drink will get lots of U.S. orders from the people who now order Soylent drinks online. If JJ can get Plenny stocked by Amazon, and if they price it even a little lower than Soylent, they will be able to compete very well in the online arena. And I think that a Huel RTD could also compete very well, again in the online arena, in the U.S. It could do in the EU against Saturo et.al. as well – setting aside Brexit unknowns.
In a recent interview I discussed here, Julian Hearn admitted to having talks with unspecified “UK Supermarkets”. If Huel can place any products, but especially an hypothetical RTD one, on the shelves at (let’s say) Tesco, that could cement its UK retail dominance just as Soylent’s move into 7-11 and Kroger stores did in the U.S.
(*) it is possible that a retail behemoth like Starbuck’s or PepsiCo might decide to enter the meal replacement field, and with their muscle they could place a competitive product alongside Soylent. However, launching a new product is expensive and chancy; the big players are more likely to enter a new market by buying an existing product. Which is why people often expect, or dread, the news that Rosa Foods has been bought by e.g. General Mills.