Not recorded and doubtful; The evacuation/migration from Noricum in 488AD is the only one recorded and seems to be a very isolated/special event in those times; What genetic impact the Noricans of Odoakers evacuation had on Italy is not known; In Eugippius it is informed that they were scattered all over Italy (not concentrated in on specific area) thus impossible to properly determine their impact and how many were left to evacuate is the other question;
Also keeping in mind however that the other provinces who had a strong Native (pre-Roman) pop. remained largely intact as such; As in the cases of prov. Britannia (which the Romans abandoned) but the native pop. remained (just getting pushed more west and some migrating into Armorica hence Brittany) or prov. Gallia whichs Gauls/Gallo-Roman pop. still remained a/the force in the Merovingian realm and the same goes for all other provinces that still had an intact population;
But the Agri Decumates and Raetia Vindelicia were scarcely populated directly before the Romans emerged (post#3) and they were frontier provinces and once the military abandoned it not much was left; A reason the Agri Decumates and Raetia Vindelicia did not have a strong (direct) pre-Roman pop. is most likely due to the Cimbric/Teutonic track a century before the Romans emerged; We know from Ptolemy (II/X) of the Helvetic-dessert in the later Agri Decumates and from Julius Caesar (De.Bel.Gal. VI/XXIII) that it was custom (greatest glory) amongst the Germanic people to utterly waste the enemies lands (desserts) or what we know from Strabo (VII/II) 'And he goes off to say that in earlier times the Boii dwelt in the Hercynian Forest, and that the Cimbri made a sally against this place, but on being repulsed by the Boii, went down to the Ister and the country of the Scordiscan Galatae, then to the country of the Teuristae and Taurisci (these, too, Galatae), and then to the country of the Helvetii men rich in gold but peaceable; however, when the Helvetii saw that the wealth which the Cimbri had got from their robberies surpassed that of their own country, they, and particularly their tribes of Tigyreni and of Toygeni, were so excited that they sallied forth with the Cimbri' which would correspond to Eutropius (V/I) that the track which reached the Rhone in 105BC was of Cimbri/Teutones/Tigurini/Ambrones and described as tribes from both Germanic and Gaulish;
Either way this could explain (Cimbric/Teutonic track) the scarcity in population between Rhine and Danube and maybe also between Alps and Danube;