Of I were in control of the series going forward, I’d just focus on remaking some of the older titles with the FOX engine tech. Realistically, fans won’t be pleased if Konami tries to create its own Metal Gear Solid game without Kojima, so their safest option is probably just to remake some of the older games and bank on fans getting overly nostalgic.
Honestly? Another collection. I would try and make a Legacy Collection caliber affair with Metal Gear Solid V added in, with 4K and/or HDR available for the titles that make sense. Metal Gear Survive is probably going to bring in some new fans with how different it is from the other games, why not take advantage of that and give players a chance to try the other games out (and make some money in the process)?
Providing Survive is a success, I'd expand on that survival-based gameplay and maybe lean on the tactical espionage action that made the series so famous. The bat-shit story of Metal Gear is ostensibly all wrapped up, so I'd wager that the franchise's future – if there is one – lies with multiplayer-focused titles. And that's despite the fact MGO struggled to leave much of an impression...twice. So perhaps a full-blown remake of MGS a la FF7 is the way to go?