Our plans to extend .NET support in UIC certainly depend on customers demand on this feature. In current IPP version (and upcoming IPP 7.0 beta) we provide just minimal sample of .NET wrapper built on top of UIC JPEG codec. It is available in source so you can extend it in case of urgent need. Note, there is sample C# JPEGView application, located in ipp-samples\image-processing\dmip which use .NET UIC JPEG codec to open images. It currently supports only baseline JPEG images.
Please let us know what application area or usage model requires you need for .NET UIC interface. What features are most important in your case.