I investigated about your issue. I successfully migrated Angry Bots project from Unity Mac 4.3 with Wwise 2013.2.8 (Build 4865) Integration to Unity 4.5.4 with Wwise 2014.1 (Build 5158) Integration.
Here are the steps i followed:
01- Create New unity project with Unity 4.3
02 - Import Angry Bots Package
03 - Once import is over, close Unity Project (don't save the scene)
04 - Open Unity 4.3
05 - You are prompted with an "Upgrading Project" Message.
06 - Click [ Continue ] Button
07 - Wait for Ugrade to complete
08 - Import Wwise 2013.2.8 (Build 4865) Integration
09 - In Wwise Installation screen, click [ … ] Button to set project path
10 - The Project I browsed to is Integration Demo provided with Wwise Mac SDK
11 - In Wwise Installation Screen, click [ Start Installation ] Button
12 - You get a Unity Warning about Audio Settings
13 - Click [ OK ]
14 - Wait for Integration to complete
15 - In Unity browser, navigate to Assets folder and open "Angry Bots"
16 - In Unity Hierarchy, click on Audio Listener under Main Camera and disable audio listener Component.
17 - In Unity menu, navigate to Edit > Project Settings > Audio and tick "Disable Audio" box (you will get a "no audio listener" message otherwise if you start your scene)
18 - In Unity menu, navigate to Assets > Wwise > Install Plugins > Mac > Debug to install plugin manually
19 - Using Wwise Picker, Add soundbank to main camera
20 - Under AkBank Component you just added, select Load On: Start
21 - Using Wwise Picker, add an event to main camera (Make Sure event is in your soundbank)
22 - Add rigidbody component if asked by Unity
23 - Under AkAmbient Component you just added, select Trigger On: Start.
24 - Close Unity 4.3
25 - Save Scene
26 - Open Unity 4.5.4
27 - Import Wwise 2014.1 Integration Package
29 - Migration Screen is displayed (BE CAREFUL: Migration screen can appear behind Unity if you remove the focus from Unity during packages import. Don't forget to right-click on Unity Icon in your Dock and select "Show all windows")
30 - Save scene if asked
31 - You get a Unity Message Asking you to Reload Project
32 - Click [ OK ]
33 - Close Unity 4.5.4
34 - Open Unity 4.5.4
34 - Play Scene: Wwise Sound Engine is Inizialized and Audio Plays.
For some reason, as Angry Bots is a quite old project, Wwise is not able to install automatically plugin at the end of migration (hence the "AkSoundEngine" error displayed in Unity console).
After reloading your project to complete the migration process, you therefore need to navigate in Unity menu to Assets > Wwise > Install Plugins > Mac and select the plugin version needed (Debug, Profile or Release) manually.
Let me know if this helps !