Aeon Genesis has also been working on Super Robot Wars Alpha for a long time, with delays largely caused by attempting to balance work on it around other projects and Real Life (combined with the fact that it isn't the easiest game to work with, from a hacking perspective).
No Export for You: Another notorious example from Japan - to date, the franchise has fifty-four distinct software products released under its banner. English-speaking players have received legal releases of only three of them - the Super Robot Wars Original GenerationGame Boy Advance installments and the first Endless Frontier; English-speakers also got a release of Super Robot Wars Original Generation: Divine Wars, but undubbed. International copyright regulations make the export of virtually any game with a licensed property in it impossible, and titles that did come over did not sell sufficiently to justify further export of the Original Generation games.
As an example, the series lineup in Super Robot Wars W consists entirely of Namco Bandai and Toei Animation-held, American-released shows. But in America, the rights for Voltron are held by World Events Productions (who have reportedly been in off-again, on-again disputes over it with Toei for the rights to make a movie), GaoGaiGar and Tekkaman Blade are Media Blasters properties, while Mazinkaiser, Martian Successor Nadesico and Full Metal Panic! were part of ADV Films and may still belong to Sentai Filmworks or Aesir Holdings. W would still be one of the simplest titles to sort out, licensing-wise. In short, the hurdles facing any SRW game legally are formidable due to the way anime sublicensing has worked and continues to work.
One of the most frustrating examples, however, would go to Super Robot Wars Alpha - Banpresto was able to get the okay from almost all the license-holders stateside to use the property, and it would have been the ideal time to release it, as Mobile Suit Gundam Wing was at the height of it's popularity. There was even a significant amount of work put in to localizing it...until the aforementioned Harmony Gold said no, not wanting Super Dimensional Fortress Macross to be brought stateside and interfere with the sales of Robotech (a series which had ended over 10 years ago). As Macross was essential to the plot, this pretty much killed any chance of the games being released.
In what can be considered a Cue the Flying Pigs statement, Namco Bandai announced in February 2016 an English localization for Super Robot Wars OG the Moon Dwellers for the Southeast Asia region. Whether that extends to Europe and North America is yet to be seen.
Pigs continue to fly with Super Robot Wars V which Namco Bandai announced would also getting an English localization for Southeast Asia, except this time, it's not an OG game.
One of Us: Hikaru Midorikawa is such a major fan of the series, he has been a beta tester for some of their games and has a page on Banpresto's official blog. To that end, any character voiced by him will have more special battle quotes against enemies. He may even throw in a few extra lines in for "his" characters for free.
Urban Legend of Zelda: The "Two Year Rule", a belief Banpresto won't include any series until two years after it ends in order to avoid Spoilers. In reality, any series can't be added until the rights come up for licensing; this rule can be disproven simply by looking at the original SRW, which had Mobile Suit Gundam F91 barely over a month after it came out in theaters.
Additionally, there was a rumor that Banpresto and Winkysoft had some kind of falling-out, which is why Masou Kishin characters haven't appeared in a mainstream game since Alpha Gaiden. This was proven false when they reappeared in the Second Original Generation.
The idea of "hybrid" robots (neither a Real Robot or Super Robot) in the games, since some units don't behave the way they should (ie: a real dealing more damage than a super or a super more accurate and agile than a real). Most players insist there's no such thing as "hybrids".
What Could Have Been: Although Space Battleship Yamato 2199 officially made it's debut in V, the series was requested earlier. However, it was shelved initially because it's not a humongous mecha anime. Had it not been shelved for this reason, Yamato 2199 might have debuted in another game.