My reply:
Jim,
Pending a thorough review of 100c, it is too early to tell if you should upgrade. Nobody has any details on 100c yet. I have attended one webinar that Sage had and the specifics are vague. There are a series of webinars coming up.
What I know is that there will be a new web based user interface. I have seen it and it looks good. This first version of 100c will contain no feature changes. The features in regular Sage 100 version 5.3 that you are currently planning on upgrading to first quarter next year are the same as in 100c. Also, 100c will be subscription based. It is like leasing the software. You pay a monthly or annual fee forever. If you fail to make a payment Sage hits the ""kill switch"" and the software becomes inoperable.
Further, your company doesn't want to be the guinea pig that finds all of the software defects in a new product. I advise waiting a year and doing another upgrade at that time if it seems worthwhile.