ESX 4.1 is the latest update, there will be no more updates than that.
A strong message is being pushed to the customers about the End of the life the ESX 4.X classic. The full blown ESX with service console. The way to go is to use the VMware Hypervisor 4.1 based on the formerly ESXi 4.1. The benefits for the customers are numerous:
01. Less patching – only about 1/10th of patches comparing to the ESX Classic.
02. Scripting scalability – by using vCLI or PowerCLI against several ESXi hosts you have more benefits than only having the scripting possibility inside of one host's COS.
03. Security – without the COS, the security is reinforced because the product is much smaller.
This version does have a small busybox console to do a management tasks, and was enhanced with local/remote TSM support mode. TSM stands for Technical Support Mode. This mode can be activated via the VI client or at the console of the server.
You then have the possibility to use a SSH client like putty, which is one of must have free tools to manage your virtual infrastructure.
There is a video from an interview between Dauglas Phillips, who interviewed Sean and Charu from the ESXi team. You'll see that the ESXi has all the necessary tools to do a troubleshooting in case you need to. Whether to use the vCLI and(or) PowerCLI installed on the management station, or also vMA 4.1 – a virtual Appliance deployed to your vCenter.
All those tools can be used to pass some CLI configuration and management commands.
Also you can have a look at the First Day Wrap up video :