Their plan for the reverie was part of their current plan, but it wasn't their whole plan. The whole plan as to why Dragon summoned all of the top execuetives (not just the main army commanders) remains unknown. But let's analyze what the RA have done so far in OP world to see what their future course of plan would be like.
1. Dragon started gaining attention for spreading his ideology 10 years ago.
2. Over the course of less than 8 years became the biggest criminal in the world, even bigger than pirates who had been ruling the seas for decades. Implying Dragon had taken some huge steps, as WG doesnt base bounty on just perceived threat, but actual threat.
3. Over the course of years, including timeskip + years before, the big 4 RA commanders had been in their own assigned oceans taking over countries and fighting WG forces/nations.
4. Whitebeard's downfall, trigerring Dragon to call the RA commanders together, which took about 2+ years to happen.
5. They gathered right before the meeting of the World Council, with 3 of the 4 commanders going with Sabo to declare war on the Gods of the World and to rescue Kuma. While other officers like Betty, ivankov, Dragon, and commander underlings stayed behind. We can assume that they had another plan had the mission gone successful. We also don't know whether Sabo is caught/dead/framed for something.
We need the following questions answered first and foremost before we can even get to what their future plans are going to be:
- What was gonna be their way of declaring war?
- What was gonna be their ways of rescuing Kuma?
- What happened to Sabo? (This is extremely crucial)
But possible things that can happen based on the info we have:
- Gaining allies like Alabasta and FMI. I don't think it's a mere coincidence that Dragons father was the one escorting FMI. Alabasta already had a revolution before and is bringing upon a change in the WG. Add on the fact that RA is fighting for the Fishmen, this is a possible scenario. There's also the Warlords to get allied with.
- Direct attack on the World Government. It's a longshot that I dont see Dragon doing until later in the manga, but who knows he might go for a direct raid for the celestial Dragons.
But it's hard to speculate without getting those questions answered first.
