Actually, that would be Decimus Junius Brutus Albinus, who was Caesar's trusted friend and legate from the Gallic Wars and also a distant cousin.
If you think about short-term events (say, the first few days), there was already a lot of strife and hatred for Decimus Brutus when it was announced he was on Caesar's will, and the announcement that he was to be the heir would not make it impossible for Decimus to be torn apart by the mobs if his gladiators aren't around (Helvius Cinna was gruesomely killed by a mob just because people thought he was Cornelius Cinna, who wasn't even a part of the conspiracy, so imagine what they could do to Decimus).
On the longer side, the situation is better when you take into account there's no Octavian to push Italy into civil war and Cicero has no real way of causing strife himself, yet Antonius has the awkward situation of having been humilliated by Caesar's will and having a mature general as his likely rival. While we know little of Decimus's motives, it can be said all of his moves from 44 to 43 BC were based on self-preservation and he has the office of Praetor Peregrinus as a safeguard and the influence of his friends (especially Trebonius as Governor of Asia, who is also a brilliant general yet in need of a friend with influence, yet even inheriting Caesar makes it unlikely he'll be sent to the Cisalpine Gaul in a legal way (he did just take over the province).
If the newly named Gaius Julius Caesar Brutus Albinus (as I think that would be the likely naming) survives the first days of public hatred, all will depend on him, Antonius, the Liberatores and the Caesarians's capacity for a reconciliation and whether Decimus is percieved as a threat or not on account of his new wealth and name.
Finally, it should be noted there are two other people involved in the testament as Caesar's great nephews, Quintus Pedius (who has already shown skill in the Munda campaign) and the mostly unknown Lucius Pinarius Scarpus. Scarpus is certainly going to play a limited role, but Pedius shouldn't be underestimated as a wildcard despite his lack of political influence with a challenged Decimus and a dead Octavian.