I've heard nothing about any EBB Nelson ever, there definitely isn't one on the horizon right now. Perhaps in the distant future, but any development for one hasnt even started yet.
New UK EBB coming next will be the missing RN EBB5, which will be a Vanguard. There is also an L1, the fate of which is undecided at the moment although we have our ideas. For more details you're probably best keeping your eyes on the test server forum sections since that is the relevant forum area for NF content that is being developed but is yet unreleased. I believe the new event ships can be seen on the test server, although all stats (R mount size, speed, DP, level) should be disregarded as everything is subject to change pre-release.
