MacOS Sierra has arrived released on the 20th Sept 2016.
Having installed it on a number of test machines over the past few days the installation has been fine. I have to say compared to El Capitan upgrade last year MacOS Sierra so far has been a great improvement.
As for hardware requirements according to Apple the following Machines will work with Sierra:
• MacBook (Late 2009 or newer)
• MacBook Pro (Mid 2010 or newer)
• MacBook Air (Late 2010 or newer)
• Mac mini (Mid 2010 or newer)
• iMac (Late 2009 or newer)
• Mac Pro (Mid 2010 or newer)
I also read the minimum Memory is like its predecessor 2GB of Ram……
Even with a SSD I think you would struggle to use the Operating System for day to day business.
I would also state that 4GB is not enough for MacOS Sierra. Most Apple machines ship with 8GB now even the Macbook Air 13″ which is a good indication that running the new Operating System 8Gb is a must for day to day use. The Macbook Air 11″ still ships with 4GB but it does have the advantage of a SSD so the combination of the 2 will ensure it works.
My advice is run all your software updated including the Safari 10 update (just been released) backup your machine with Time Machine then download the installer and run the upgrade. Depending on the machine specs depends on how long it will take. The SSD machines I have installed it on took around 30 – 45 Min to install. The standard iMac or mac Mini took longer but again only about 1 hour to install. Once completed it goes through the wizards to ask you about Siri and iCloud backups of your documents folder. On that subject if you don’t need to have a backup of your documents on the cloud then I would cancel that as it will no doubt ask you to sign up to the apple subscription service starting at .79p per month.