Hunnic hegemony can't really be considered as an empire, in the sense of an unified authority on a territory, and peoples living on it.
What existed was rather a personal construction, led by a charismatic leader on several different
peoples (mainly German, then Iranian, and some Huns) and with an unstable aristocracy (without the presence of what is a Late Antiquity
imperium or what it implies, such as taxes and absence of fixed social roles) made in good part of Romans.
The degree of submission, and not really integration (more like political-military alliances between different cohesive peoples and groups), of these peoples varied, but Hunnic hegemony wasn't that strong compared to its importance in the mid-Vth century.
It didn't litterally disappeared overnight but, frankly, almost so :
Nedao is a good enough exemple on the relative superficial domination of Huns, as a political and personal alliance and chain of obligations.
Attila's power in particular, and Hunnic dominance in general eventually came down to two features, namely the unicity of royal power since Ruga and the redistribution of Roman gold, from tribute and/or plunder.
For that it survives Attilla's death, we should gave a look at how Barbarian ensembles and leagues as Franks, Goths or Vandals worked out, rather than Avars or Mongols*. It implies necessarily military successes and deeper integration in Romania' politics (more than a predatory mindset that is)
I would tend to think that killing Attila in 449 (IOTL, the assassination attempt failed) or slightly later would help : a less ambitious and "hunnic"-minded leader could better fit these, more or less pulling a Dengizich but at a point where it could be viable.
Let's be blunt tough, it would have relativly little macro-historical impact historically : I could see well a more limited Hunnic hegemony replacing Upper Danubian peoples (as Herulii, Lombardii, etc.) and heavily "germanized" (
meaning heavily romanized as well).
Basically, germano-roman agglomeration of peoples, whom ethnogenesis would be based on their contact with Romania, and that would keep the ethnonym of "Huns" or maybe identify themselves as "Scythians", and establishing themselves in Romania either creating their kingdom in Romania (Italy or Illyricum, maybe Moesia or on its marches (as Gepids IOTL) along Danube.
Of course, at this point, there's nothing really allowing this *Hunnic Kingdom, to be more prone to survive than other trans-danubian petty-kingdoms or states as Heruli or Gepids did IOTL, would it only because they would be stuck between incoming entities as Kurtigurs or Avars from one hand, and cisdanubians states as Italy and Romania.
Eventually, maybe they could fill the role Lombards did, for exemple, for Constantinople as in a ready-to-use vassalized people, but it's obviously not a self-evident outcome.
*Whom, in spite of an heavily racialized historiography, they shared little with.