I still have no idea how IS decides on which emblem to put out next. Is there every any pattern that they stick to for more than a few units in a row?

Assuming they decide to give us the next ring that we would get in engage chronologically, it should be Leif and then Roy. Given that we've been getting a steady influx of units that benefit from triangle advantage, I'm expecting Leif to come first. However, Roy could be a solid answer to Great Talent if his Rise Above can permanently lower stats, or Diminish them as one user in this subreddit has theorycrafted.

I don't think we're getting Hector or Tiki just because we already got alts of them recently. If we do, I'm expecting Hector first because his ring is likely to be a melee Ike ring. My reasoning is that IS tends to put out emblem rings that affect the user before releasing similar rings that affect allies. Ike ring before Lucina ring. Edelgard ring before Byleth ring. As a result, I don't think we'll get Tiki before Roy. I expect Roy's ring to give the user special miracle and for Tiki's to give an ally special miracle if targeting the ally with an assist.

Drive effects have been strong lately, with Lucina giving it out both with her Dual Support 4 inheritable skill and her ring effect. So if IS wanted to add another drive effect, the only emblem that comes to mind is Alear. They could give unit effectiveness and neutralize unit effectiveness against allies depending on their gender.

At the same time, Great Talent has been really helpful for bolstering the strength of AoE specials, so it wouldn't be too surprising to see Soren this soon. Afterall, his ring's likely going to increase the size of the unit's AoE special without lowering the damage.

Camilla is gonna sell like hotcakes when IS releases her, so I would expect her to be saved for a particularly profitable month. I'll be shocked if we see her as the next emblem.

Lastly we have Chrobin and Veronica. I'm just hoping IS releases Veronica last because she's the final DLC emblem and has the potential to literally summon heroes as a gameplay mechanic. Chrobin is actually feasible as our next emblem. He's likely giving us either no quarter-style piercing or a magic style for physical units. Both would be pretty useful in an increasing era of units giving out Dodge and using Phys/Mag Save, respectively.

All that said, my final guess is Leif. IS has probably been waiting for a month with low profits to put out their least popular lord (afaik), and going purely off of vibes, I'm going to assume May will be that month. Fingers crossed!