Why is there no confirmation? We've seen him get rid of opponents wind magic and evaporate water before, so thats enough to say he could well make those sorts of attacks from God Serena moot. I'll remind you Natsu was holding back a lot before he and Jacob got outsidethe guild, where he finished Jacob off with one shot, and as for the GOI, there is nothing concrete to say they're actually stronger than GMG Jura; its just speculation. I really don't see how people say God Serena could win when Natsu has essentially one-shotted a Spriggan when he stopped holding back (A Spriggan > God of Ishgar any day of the week), it really does seem like he's being overrated a fair bit when Natsu makes three out of his four elements (that he's shown) moot (Can Dispell the hurricane one with FDKM heat, evaporate the Sea King attack, eat Serena's purgatory dragon attack) which leaves Serena with his Earth Dragon Slaying magic which really is the least impressive out of the attacks that we saw.You've got to be KIDDING me. So much speculation and assumption here. Power-up? dispelling wind/water is a possibliity but there's no confirmation that he can do that even if he can "melt the surrounding landscape". For all we know, the only reason he could burn Zeref's magic was due to Igneel's flames,not BASE FDKM.
Natsu needed help to defeat Jacob (JACOB). Whereas God Serena defeated FOUR people above GMG Jura level (I assume Jura's gotten a bit more powerful) WITHOUT breaking a sweat. Like seriously. At best, Natsu with no BS plot armor in Dragon Force at this point might lose mid-diff at best.
After his many pitiful showings, Bluenote isn't close GMG Jura/Laxus level.
Now, while some might say Serena could have resistance to Natsu's fire, Serena hasn't shown he can mix his elements in his attacks which means if he wants to win he has to let go of having the resistance to use other attacks, which puts him in line to really take some damage from Natsu's attacks. Now that I think about it, what is there to actually say he takes on each element as a mode? He literally just uses spells of different elements and hasn't shown he can take on further properties of the dragon, so Serena could possibly not be able to get resistance to Natsu's fire at all. Serena isn't dedicated to one element, so there's got to be some disadvantage to having that many lacrima/different elements, and not being able to eat other elements or take on more properties from an element could well be the case with Serena. So again, it really is silly to say Serena 'stomps' Natsu etc. when Natsu has greater attack, defense and speed.